Astronomers discover a “hidden” black hole outside the Milky Way – Galileo Magazine

With the help of data obtained by the MUSE instrument, installed on the Very Large Telescope (VLT) in Chile, astronomers have found a small black hole in an unexpected region: outside the Milky Way. This is the first time that the European Southern Observatory (ESO) instrument has been able to detect black holes outside our galaxy – in this case, the object was located about 160,000 light-years away from the Large Magellanic Cloud, a dwarf galaxy orbiting it. Milky Way.

This isn’t the first time stellar black holes have been seen in galaxies outside our own. However, previous discoveries have come from capturing X-ray glare or gravitational waves emitted when these celestial bodies “swallow” matter or collide with each other. The problem is that most stellar-mass black holes cannot be detected by X-rays or a gravitational wave.

Only the presence of most of them is detected, as Stefan Drisler explains, “dynamically”: “When they form a star system, they affect its motion in a subtle but detectable way, until we can find it with sophisticated instruments,” explains an astrophysicist from the University of Göttingen, Germany. and co-author of the study, in the statement.

Discovery leader Sarah Sarasino compares the method used to the investigations of famed fictional detective Sherlock Holmes in search of criminals. “We look at each star in this group as if we were holding a magnifying glass in one hand, trying to find some evidence of black holes, but without seeing them directly,” says the scientist at the Astrophysical Research Institute, in the United Kingdom.

It was the gravitational effect of a black hole on the star it orbits that caught the researchers’ attention. The celestial body has been found waiting in a star cluster known as NGC 1850, located about 160,000 light-years from the Large Magellanic Cloud. It is about 11 times more massive than the Sun, a size considered small.

Searching for black holes outside the Milky Way

And this discovery may be just the beginning of a successful search for stellar black holes outside the Milky Way. This is because the ESO installation, scheduled to begin its activities in 2030, could facilitate the discovery of these celestial bodies. The team estimates that the instrument will make it possible to observe stars “much weaker in the same field of view” and track black holes in groups located at much greater distances.

The array of optical telescopes, especially MUSE, is also seen as a way to study the evolution of young black holes. The newly discovered phenomenon was the first to be found in a cluster in NGC 1850: it is only about 100 million years old, in the blink of an eye on astronomical scales. Drezler predicts that “the score represents only one of the wanted ‘criminals’, but when you find one, you’re on your way to discovering more, in different combinations.”

The study was accepted for publication in the scientific journal Monthly Notices of the Royal Astronomical Society.